The present invention relates to tape printers which form a full color image on a heat-sensitive ray-responsive printing medium which is colored with heat energy and whose coloring is stopped by irradiation of rays of a specified wavelength, and a printing medium containing a cassette settable in such tape printer.
Conventionally, various printing systems have been proposed. Typical printing systems put to practical use in offices or households at present are an electronic photograph system, an ink-jet system, and in thermal system.
Recently, the demand for a color printing image has increased. Any one of the above-mentioned printing systems has improved in various respects so as to satisfy the demand for a color printing image and its printing quality has reached a sufficiently practical level. Recently, in addition to improvements to the printing quality, further inexpensive printing devices are desired.
A dominant printing method employed at present in the respective printers of the above systems is to use a cut sheet of paper to print data on it and not to print vouchers/added-up data mainly on continuous paper as in the past, from a standpoint of high speed printing and document printing. Among the above printing systems, printing mechanisms of the thermal system are very frequently incorporated into printers which are intended for cost reduction or into printers enough to perform small-sized printing because the structure of their thermal heads which perform printing is simple.
The printers of the thermal system include ones of a heat-transfer system using an ink ribbon and of a heat-sensitive system using heat-sensitive paper used generally, for example, in fax. The printers of the heat transfer system are mainly employed for color printing. However, in the case of the printers using an ink ribbon, generally, its printing rate is about 5% even when sentences are printed, for example, using a monochromatic (for example, black) ink ribbon, so that 95% of the ink ribbon is discarded without being used. Thus, the ink ribbon is wastefully used. Much more in the color printing, the respective colors of a plurality of color ink ribbons have been used only partially as the colors of the whole paper surface and discarded, so that the ink ribbons have been given a wide berth as producing very much waste. Recently, the ink-jet systems have gained power as simple color printers, but must be improved in terms of oozing and drying of the printing ink.
In such background, a new printing system which records (forms) a full color image, using a printing medium which includes three (yellow, magenta, cyan) heat-sensitive coloring layers formed on an appropriate sheet-like base material on the basis of the above-mentioned heat-sensitive system, is proposed by Japanese Patent Publication Tokkohei 4-10879 and 6-51425, and put partially to practical use. The yellow or magenta coloring layer includes a color former coated uniformly on a base material. The color former includes a dispersed phase in which compounds containing in molecules active methylene called a coupler and a diazonium salt exist in a mixed manner as particles on the order of micron. The couplers are activated by heat of a predetermined temperature or more so that the compounds and the diazonium salt react in a basic atmosphere to form a yellow or magenta coloring matter. The diazonium salt is dissolved with rays of a specified wavelength (ultra-violet rays) to lose the function of reacting with the couplers. The cyan coloring layer includes a color former coated uniformly on the base material, the color former including a dispersed phase in which particles of leuco coloring matters on the order of micron and developers exist in a mixed manner. This cyan layer reacts with the aid of heat of a predetermined temperature or more to be colored.
FIG. 25 shows one example of conventional heat-sensitive recording devices (printers) which form an image on the above-mentioned printing medium (heat-sensitive ray-responsive recording paper), disclosed in Japanese Patent Publication Tokkohei 6-51425.
In the heat-sensitive recording device of FIG. 25, a roll of recording paper 1 is brought at a portion 1' into close contact with the peripheral surface of a drum 3 through a paper feed roller 2, and the recording paper portion 1' is then carried by the drum 3 in a direction of arrow n or r below a thermal head 4 and a light source unit 5. The thermal head 4 extends in the form of a line along the longitudinal axis of the drum 3 (perpendicular to the face of the FIG. 25 sheet). The light source unit 5 includes in a housing 5a a light source 5b which emits rays in a predetermined frequency band and a filter 5c provided below the light source 5b which selects rays of each of different wavelengths corresponding to yellow and magenta to irradiate the recording paper with the rays. Feed rollers 6, a cutter 8 and a discharged paper tray 7 are provided to the right of the dram 3.
FIG. 23 is a cross-sectional view of recording paper used in the heat-sensitive recording device. FIG. 24 shows the relationship between the coloring density of each of the coloring layers of the recording paper and heat energy applied to that coloring layer.
The recording paper 1 of FIG. 23 is of a heat-sensitive ray-responsive type and includes paper of three heat-sensitive coloring layers; that is, a yellow layer 1--1, a magenta layer 1-2, a cyan layer 1-3 layered uniformly on a sheet-like supporting base material 1-4 with a heat-resistive protective layer 1-5 provided on the yellow layer 1--1. In each of the yellow, magenta, and cyan layer 1--1, 1-2 and 1-3, its main coloring materials contained in small heat-responsive capsules of a diameter of about 1 .mu.m are distributed along with other components in a binder material. As shown in FIG. 24, in order to control coloring of three primary colors with heat energy, the heat sensitivities of the respective couplers are designed so as to decrease in order of yellow (Y), magenta (M) and (C) layers (that is, the yellow layer is colored at the lowest temperature) to thereby record image data on the basis of coloring of yellow, magenta and cyan. However, if such heat sensitivity differences are only provided for the respective layers, and even when, for example, only magenta is intended to be colored, magenta as well as yellow would be colored because heat energy required for coloring the magenta will necessarily color even yellow which requires less coloring heat energy than the magenta. Thus, a desired color cannot be obtained. In order to avoid this problem, the upper two layers contain in a mixed dispersed manner components that prevent the upper two layers from being colored by the respective next higher coloring heat energy after the upper two layers are respectively colored, or nullify their colorability by respective rays of specified wavelengths (ultraviolet rays), that is, fix their colored states.
Thus, first, in FIG. 25, the thermal head 4 selectively produces a heat quantity suitable for a coloring layer which is colored at the lowest temperature (ordinarily, the yellow coloring layer) while coloring a corresponding (yellow) image on a recording paper portion 1' carried in the direction of arrow n by a forward rotation of the paper feed roller 2. The roller 2 then feeds out the recording paper 1 until the recording paper portion on which the (yellow) image has been colored reaches at its trailing end a position below the power source unit 5. The paper feed roller 2 is then rotated in a reverse direction to carry the recording paper 1' in the direction of arrow r while the light source 5b emits with ultraviolet rays of a specified wavelength whose emission peak is 420 nm onto the first layer (yellow colored layer) of the just colored recording medium paper portion through the filter 5c from the light source 5b, the ultraviolet rays acting only on the first layer, to dissolve the (yellow) color former so that no more (yellow) color former thermally reacts, that is, to stop the coloring of the background of the (yellow) colored image to thereby fix the (yellow) image. The recording paper portion 1' is carried intact reversely in the direction of arrow r to the position where the (yellow) image started to be colored.
Then, the paper feed roller 2 is again rotated in the forward direction to carry the recording paper portion 1' in the direction of arrow n while the thermal head 4 is selectively producing a heat quantity suitable for a layer colored at the second lowest temperature (ordinarily, the magenta's coloring layer) to color a corresponding (magenta) image on the recording paper portion 1'. Also, in this case, the recording paper portion 1' on which the (magenta) image has been colored is fed out so that the trailing end of the image reaches below the light source unit 5. Then, the paper feed roller 2 is rotated in the reverse direction to carry the recording paper portion 1' reversely in the direction of arrow r while the light source unit 5 is irradiating only the second just colored (magenta) layer with ultraviolet rays of a specified wavelength (whose emission peak is at 365 nm) to dissolve the (magenta) color former so that no more (magenta) color former performs a heat-sensitive reaction or that the coloring of the background of the colored (magenta) image is stopped to thereby fix the (magenta) image superimposed on the previously formed (yellow) image. The recording paper portion 1' is then carried reversely or in the direction of arrow r to the position where the recording paper portion 1' started to be colored first (or where the yellow image was colored).
Then, the paper feed roller 2 is also rotated forwardly to carry the recording paper portion 1' in the direction of arrow n while the thermal head 4 is selectively producing a large quantity of heat suitable for the last (ordinarily, cyan (C)) coloring layer to form a corresponding (cyan) image on the two already fixed (yellow and magenta) images in the superimposing manner to thereby produce a full color image.
As described above, the recording paper portion 1' on which the full color image has been formed is carried intact in the direction of arrow n, moved away from the drum 3 by the feed rollers 6 provided downstream in the carrying direction, and then sent to the discharged paper tray 7. The recording paper 1' is then cut by the cutter 8 provided upstream of the discharged paper tray 7, and piled on the discharged paper tray 7. The heat-sensitive recording device disclosed in this prior art discloses the principle of the recording method, but not control for irradiating the recording paper portion 1' with accurately from the light source unit 5 and a method for avoiding exposure of an unused portion of the recording paper 1, and various problems to be solved for putting the device to practical use still remain.
Printers which utilize the convenience of the thermal type printers and which are intended to be used in a different manner from that of the above printers have appeared and started to be used widely as business or household ones. These printers each comprise an input unit, a display unit and an output unit so that characters are printed on a long printing medium tape wide about 10-50 mm with an ink ribbon. Generally, a tape cassette which contains a set of such printing medium tape and ink ribbon, as mentioned above, is removably set on each such printer in use.
FIG. 26 shows a main portion of such conventional tape printer in a cross-sectional view in which a tape cassette 12 set in a tape cassette accommodating space 11 in the tape printer 10 comprises a paper reel 13, a ribbon feed reel 14 and a ribbon winding reel 15 with a printing paper tape 16 in the form of a roll formed around the paper reel 13 and an ink ribbon 17 in the form of a roll formed around the ink ribbon feed reel 14. The paper reel 13 is engaged in its hole 13a over a paper reel drive shaft of the printer to be rotated forwardly or backwardly (clockwise or counterclockwise in FIG. 26). The ribbon winding reel 15 is engaged in its hole 15a over a winding reel drive shaft of the printer to be rotated forwardly (clockwise or in the paper carrying direction in FIG. 26).
The ribbon feed reel 14 is engaged over a brake shaft of the printer so that its rotation is braked as requested. A pair of cutting blades 18a and 18b is provided each on a respective side of a paper discharge port provided on the right-hand side of the cassette accommodating space 11 (FIG. 26) in the tape printer 10 to cut away the printed paper portion 16' to be discharged to the outside.
When the tape cassette 12 is set on the printer, as shown in FIG. 26, the thermal head 21 fixed and supported at one end of a bracket (not shown) of the printer body is inserted into a recess 19 formed in the tape cassette 12. The thermal head 21 turns counterclockwise around a pin 21a within the recess 19 by the counterclockwise turning operation of the bracket to press the paper 16 and ink ribbon 17 against the platen 22 whereas the thermal head 21 turns clockwise to move away from the printing position in the non-printing operation.
The paper 16 is fed out from the paper reel 13 into the printing section where the thermal head 20 and the platen 22 face each other. The ink ribbon 17 is pulled out from the ribbon feed reel 14 by the winding operation of the ribbon winding reel 15 to extend under the paper 16 across the recess 19 and a printing ink in the ribbon is transferred by the thermal head 21 to the paper 16. The paper 16 on which an image is now formed with the transferred ink is then discharged as the printed paper portion 16' to the outside and cut away in an appropriate length by the pair of cutting blades 18a and 18b.
The printed paper (tape), as shown in an enlarged broken line circle A in FIG. 26A, usually has an adhesive layer b and a peelable paper strip c provided on a back of a printing medium a. By removing the peelbable paper strip c from a cut printed tape 16', the printed tape can be pasted, for example, on one of user's belongings, a book, a video cassette or a locker at a desired position in use.
Generally, the tape cassettes 12 used widely comprise a combination of a predetermined background color tape (usually, a resin film tape) and a monochromatic (for example, black) ink ribbon. Recently, tape cassettes which each contain a multi-colored ink ribbon have appeared so as to satisfy a demand for color printing.
Even with such tape cassette, production of waste of ink ribbons cannot be avoided. Tape printing, however, has been accepted because the quantities of paper and ink used are not so large as a whole. With such tape printers, a combination of tape and ink ribbon is used. Thus, although the quantity of paper and ink used is small, the tape and ink ribbon are designed so as to be both used up simultaneously in length in consideration of economic efficiency. However, it is substantially impossible that both the tape and ink ribbon are used up simultaneously as designed because of various mistakes or accidents occurring in use mainly on the user side, and hence the production of tape or ink ribbon waste cannot be avoided.
In such tape printer, a quantity of tape contained in the tape cassette decreases because of a space which the ink ribbon occupies in the tape cassette. Thus, a frequent exchange of a tape cassette is compelled. Although separate setting and removal of the tape and ink ribbon has been proposed, the composition of a mechanism for this operation as well as their handling is complicated and troublesome. Thus, it is not practical.
Since the tape printer of this type prints characters with the thermal head, it can use heat-sensitive paper like a FAX device. In that case, a tape cassette which only contains a printing tape without an ink ribbon may be used, and hence it seems that the above problem is solved. Since there are actually no heat-sensitive tapes which satisfy color printing sufficiently, the printer cannot form a satisfactory color image. Thus, the color ink ribbon system has been established for the color orientation and it is impossible to grow out of the color ink ribbon system. Furthermore, there have been no ideas themselves which solve the above problems.
When a new printing system is employed, especially in a tape printer, proper design is required to adjust the new printing system to the structure of the printer based on special specifications for the tape printing. More particularly, if the above-mentioned various problems are considered, it seems to be a first step of solving the problem to use a printing system based on the above-mentioned heat sensitive system. However, mere employment of new materials will not suffice, but there are various problems to be solved such as ray irradiation control, a method of mounting a printing mechanism, a tape carrying mechanism, its control method, a tape cassette structure, etc., for putting the tape printer to practical use.